Abstract: We systematically investigated the electrical properties of the tris (hydroxymethyl) aminomethane crystal, a new type of pyroelectric crystal material. The properties studied are the dielectric constant, AC-and DC-resistivity, loss angle, and the phase transition character in the orientation of non-polar axes as well as transparence. The p/ε₀ is about 10^-10. It may be expected that it would be useful in the application to infrared pyroelectric detectors.